U.S. patent application number 11/993494 was filed with the patent office on 2010-02-25 for method for sterilizing preforms and installation for producing sterile bodies from these preforms.
This patent application is currently assigned to SIDEL PARTICIPATIONS. Invention is credited to Eric Adriansens, Stephane Hebert.
Application Number | 20100047120 11/993494 |
Document ID | / |
Family ID | 35788387 |
Filed Date | 2010-02-25 |
United States Patent
Application |
20100047120 |
Kind Code |
A1 |
Adriansens; Eric ; et
al. |
February 25, 2010 |
METHOD FOR STERILIZING PREFORMS AND INSTALLATION FOR PRODUCING
STERILE BODIES FROM THESE PREFORMS
Abstract
The invention relates to a sterilization method and to an
installation (10) for producing sterile bottles (14) by blow
molding sterilized preforms (12) according to the method,
characterized in that, at the spraying station (28), the flow (F)
of sterilizing product is atomized onto each preform (12) whose
temperature (T1) is less than the condensing temperature (Tc) of
the sterilizing product so that a film of mist of the sterilizing
product deposits by condensation at least onto the inner wall to be
sterilized, and is characterized in that, at the activation station
(50) of the sterilizing product of the sterilizing unit (26), each
preform (12) treated in the aforementioned manner is heated by
radiation to a temperature (T2) greater than or equal to the
activation temperature (Ta) in order to sterilize at least the
inner wall of the preform (12).
Inventors: |
Adriansens; Eric; (Octeville
Sur Mer, FR) ; Hebert; Stephane; (Octeville Sur Mer,
FR) |
Correspondence
Address: |
YOUNG & THOMPSON
209 Madison Street, Suite 500
Alexandria
VA
22314
US
|
Assignee: |
SIDEL PARTICIPATIONS
OCTEVILLE SUR MER
FR
|
Family ID: |
35788387 |
Appl. No.: |
11/993494 |
Filed: |
June 8, 2006 |
PCT Filed: |
June 8, 2006 |
PCT NO: |
PCT/EP2006/063006 |
371 Date: |
February 13, 2008 |
Current U.S.
Class: |
422/22 ;
425/526 |
Current CPC
Class: |
B29B 2911/14033
20130101; B29B 2911/14106 20130101; B29C 49/06 20130101; B29C 49/42
20130101; B67C 2003/227 20130101; B29C 49/4205 20130101; B29C 49/46
20130101; A61L 2/208 20130101; B29B 2911/14026 20130101; B29B
2911/14133 20130101; B29B 2911/1404 20130101; B29B 2911/1402
20130101; B29C 2791/005 20130101; B29K 2067/00 20130101; A61L
2202/23 20130101 |
Class at
Publication: |
422/22 ;
425/526 |
International
Class: |
B29C 49/42 20060101
B29C049/42; B29C 49/46 20060101 B29C049/46; A61L 2/16 20060101
A61L002/16 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 24, 2005 |
FR |
0551752 |
Claims
1. A sterilization method, for sterilizing a plastic preform
intended to be molded, especially by blow molding, in an
installation (10, 10') producing sterile bottles (14), which method
is characterized in that it comprises at least the steps
consisting, in succession: (a) in checking that the preform (12) is
at a temperature (T1) below the temperature (Tc) of condensation of
the sterilizing agent; (b) in spraying a flow (F) of sterilizing
agent in the form of a vapor jet onto the preform (12) so as to
cause a substantially uniform film of a mist (52) of the
sterilizing agent to be deposited by condensing on at least one
internal wall (15) of the preform to be sterilized; and (c) in
radiatively heating the preform (12) thus treated in order to bring
it to a temperature (T2) equal to or above the temperature (Ta) for
activating the sterilizing agent so as to sterilize at least the
internal wall (15) of the preform.
2. The sterilization method as claimed in claim 1, characterized in
that it includes an additional sterilization step consisting: (d)
in spraying a flow (F) of sterilizing agent in the form of a jet of
vapor onto the preform (12) preheated to the specified temperature
(T2).
3. The sterilization method as claimed in claim 1, characterized in
that the temperature (T2) to which the preform (12) is heated is
substantially equal to the temperature (Tm) at which the preform
(12) is blow-molded, which temperature is respectively above the
activation temperature (Ta) and above the evaporation temperature
(Te) in order to eliminate the sterilizing agent by
evaporation.
4. An installation (10, 10') for producing sterile bottles (14)
from plastic preforms (12) by implementing the method of
sterilizing the preforms (12) as claimed in claim 1, of the type in
which the preforms (12) are conveyed inside the installation (10,
10') as a continuous flow, which runs from the upstream end toward
the downstream end, and of the type comprising, in succession, at
least: a sterilization unit (26) having at least one spray station
(28), called the first station, provided with at least one nozzle
(40) for spraying, during the treatment, a flow (F) of sterilizing
agent in the form of a vapor jet onto each preform (12) to be
sterilized; and a forming unit (30) comprising a thermal
conditioning station (32), which includes an oven (42) intended to
bring each preform (12) to a molding temperature (Tm), and a
molding station (34) capable of producing a sterile bottle (14),
characterized in that, at the first, spray station (28), the flow
(F) of sterilizing agent is vaporized on each preform (12), the
temperature (T1) of which is below the condensation temperature
(Tc) of the sterilizing agent so that a substantially uniform film
of a mist (52) of the sterilizing agent is deposited by condensing
on the internal wall (15) to be sterilized, and in that the
sterilization unit (26) includes an activation station (50) for
activating the sterilizing agent, comprising radiative heating
means constituting the oven (42) for heating each preform (12) thus
treated to a temperature (T2) equal to or above the activation
temperature (Ta) so as to sterilize at least the internal wall (15)
of the preform (12).
5. The installation (10, 10') as claimed in claim 4, characterized
in that the heating means of the activation station (50) consist of
the oven (42) of the thermal conditioning station (32) so that each
preform (12) is heated to a molding temperature (Tm) which is
respectively above the activation temperature (Ta) of the
sterilizing agent and above the evaporation temperature (Te) in
order to eliminate the sterilizing agent by evaporation.
6. The installation (10, 10') as claimed in claim 5, characterized
in that the molding station (34) of the forming unit (30) includes
at least one mold (44) and at least one associated blowing device
(46) which subjects each preform (12) to an internal overpressure
so that each sterilized preform (12) takes the form of the
impression of the mold (44) in order to produce the sterile bottle
(14).
7. The installation (10, 10') as claimed in claim 4, characterized
in that the mean spray axis (A2) along which the nozzle (40) for
vaporizing the sterilizing agent sprays the latter toward the neck
(16) is generally parallel to the axis (A1) of the preform (12)
during treatment and radially offset relative to the axis (A1) of
the preform (12) so as to produce a laminar flow of sterilizing
agent inside the preform (12).
8. The installation (10, 10') as claimed in claim 7, characterized
in that, in the sterilization unit (26), the preforms (12) are
generally aligned along a longitudinal run direction (X1) and are
placed in the upright position, so as to be mutually parallel side
by side, and in that the spray axis (A2) of the nozzle (40) is
radially offset along a direction approximately orthogonal to the
run direction (X1).
9. The installation (10, 10') as claimed in claim 4, characterized
in that the sterilizing agent consists of a compound containing
hydrogen peroxide or vaporized hydrogen peroxide, which is
activated by heating the preform (12) above the activation
temperature (Ta).
10. The installation (10, 10') as claimed in claim 9, characterized
in that the sterilizing agent comprising hydrogen peroxide is
sprayed in the vapor state at a temperature above one hundred and
six degrees Celsius.
11. The installation (10, 10') as claimed in claim 4, of the type
comprising at least one transport device (54) provided with means
(56) for gripping the neck (16) of each preform (12) in order to
convey the flow of preforms (12) through the oven (42),
characterized in that the transport device (54) comprises at least
one means (58), such as an internal core, which penetrates axially
into the neck (16) of each preform (12), partly or completely
obstructing the inner opening (22) bounded by the neck (16) so as
to increase the degree of sterilization by increasing the time
during which the internal wall (15) of the preform (12) is exposed
to the sterilizing agent.
12. The installation (10') as claimed in claim 4, characterized in
that the sterilization unit (26) includes, downstream of the oven
(42), a spray station (29), called the second station, which is
intended to spray a second flow (F) of sterilizing agent onto each
preform preheated to a defined temperature (T2) which is at least
above the activation temperature (Ta) and above the evaporation
temperature (Te) of the sterilizing agent.
13. The sterilization method as claimed in claim 2, characterized
in that the temperature (T2) to which the preform (12) is heated is
substantially equal to the temperature (Tm) at which the preform
(12) is blow-molded, which temperature is respectively above the
activation temperature (Ta) and above the evaporation temperature
(Te) in order to eliminate the sterilizing agent by
evaporation.
14. The installation (10, 10') as claimed in claim 5, characterized
in that the mean spray axis (A2) along which the nozzle (40) for
vaporizing the sterilizing agent sprays the latter toward the neck
(16) is generally parallel to the axis (A1) of the preform (12)
during treatment and radially offset relative to the axis (A1) of
the preform (12) so as to produce a laminar flow of sterilizing
agent inside the preform (12).
15. The installation (10, 10') as claimed in claim 6, characterized
in that the mean spray axis (A2) along which the nozzle (40) for
vaporizing the sterilizing agent sprays the latter toward the neck
(16) is generally parallel to the axis (A1) of the preform (12)
during treatment and radially offset relative to the axis (A1) of
the preform (12) so as to produce a laminar flow of sterilizing
agent inside the preform (12).
Description
[0001] The invention relates to a method of sterilizing preforms
and to an installation producing sterile bottles from the preforms
sterilized by this method.
[0002] The invention relates more particularly to a method of
sterilizing a plastic preform intended to be molded, especially by
blow molding, in an installation producing sterile bottles.
[0003] The invention also relates to an installation for producing
sterile bottles from plastic preforms by implementing the method of
sterilizing preforms according to the invention, of the type in
which the preforms are conveyed inside the installation as a
continuous flow, which runs from the upstream end toward the
downstream end, and of the type comprising, in succession, at
least: [0004] a sterilization unit having at least one spray
station provided with at least one nozzle for spraying, during the
treatment, a flow of sterilizing agent in the form of a vapor jet
toward the neck of each preform to be sterilized; and [0005] a
forming unit comprising a thermal conditioning station, which
includes an oven intended to bring each preform to a molding
temperature, and a molding station capable of producing a sterile
bottle.
[0006] Such a type of installation is described and shown in
particular in document US-A-2001/0010145.
[0007] This type of installation has the drawback of requiring a
high flow rate of sterilizing agent and/or a high pressure for
injecting the sterilizing agent in order to succeed in completely
covering the internal walls of the preforms, so as to completely
sterilize the inside of the preforms.
[0008] As a consequence, the installation therefore consumes a
large amount of sterilizing agent and the sterilization operation
is expensive.
[0009] In addition, the use of a high flow rate of sterilizing
agent may result in residual droplets of sterilizing agent being
deposited on the internal walls of the preforms. Now, when the
preforms are being heated, these droplets produce a magnifying
glass effect on the thermal heating radiation, resulting in the
appearance of stains on the walls of the bottles obtained from the
preforms in question.
[0010] Specifically, in the installations of the prior art, the
sterilizing agent is generally sprayed in the form of a mist and
with a pressure obtained by compressing a gas, such as air
compressed to pressures of about 2 to 3 bar, which is sterilized
and heated, for example to a temperature of around 130.degree. C.
so as to thermally activate the sterilizing agent.
[0011] This is the reason why droplets of sterilizing agent form an
excess which is not entirely vaporized during heating, so that each
droplet causes a local chemical attack of the preform material,
generally polyethylene terephthalate (PET), by the sterilizing
agent.
[0012] This phenomenon causes stains to appear on the walls of the
bottles, this visual defect being sometimes called "orange peel"
defect.
[0013] In addition, the walls of the preforms are not uniformly
covered by the droplets of sterilizing agent, so that regions
between each of the droplets on the surface of the internal and/or
external walls of the preform remain unsterilized.
[0014] Furthermore, depending on the profile of the internal wall
of each preform, it is not always possible to reliably reach the
bottom of the preforms, even with a high flow rate and/or a high
pressure, because of the creation of an overpressure plug at the
bottom of the preforms.
[0015] Such a type of installation is also described and shown in
document WO-A2-99/03667, which relates to a method for
manufacturing sterile plastic containers and to an installation for
implementing it.
[0016] The installation includes a device for bringing preforms to
heating means, upstream of which device the preforms are treated,
at least on the inside of the preforms, by sterilization means.
[0017] The sterilization means comprise in particular a
sterilization agent, such as a chemical solution of hydrogen
peroxide (H.sub.2O.sub.2) that can be thermally actuated,
especially through the heat of the heating means, before being
eliminated by evaporation.
[0018] The sterilization means include, for this purpose, a sprayer
formed by a spray gun that allows the inside of the preforms to be
wetted with "cold" sterilization agent, that is to say one that has
not been preheated and is therefore in the liquid state.
[0019] In the installation described in that document, the spray
gun is typically a gun of the two-fluid type, having a liquid
nozzle and an air nozzle which together form a circular spray
assembly which can be placed above the path of the preforms so as
to spray a mist of sterilization agent.
[0020] The spray of sterilization agent is formed as a cloud of
droplets that is sprayed by the spray gun onto the inside of the
preform as a turbulent flow.
[0021] It has been found that such a turbulent flow of
sterilization or sterilizing agent inside the preform results in
the formation of a number of droplets that are not uniformly
distributed over the internal wall of the preform.
[0022] This is because the use of a spray gun is characterized in
particular by a high flow rate of sterilizing agent, obtained by
compressing a gas, such as air compressed to pressures of about 2
to 3 bar, so that it produces a turbulent flow.
[0023] Now, a turbulent flow results in nonuniform deposition of
residual droplets of sterilizing agent on the internal walls of the
preforms. In addition, the droplets of sterilizing agent form an
excess that is not entirely vaporized during heating.
[0024] These droplets of sterilizing agent therefore cause, on the
one hand, local chemical attack of the material of the preform,
generally polyethylene terephthalate (PET), and, on the other hand,
while the preforms are being heated, produce a magnifying glass
effect on the thermal heating radiation, thereby causing the
appearance of stains on the walls of the bottles obtained from the
treated preforms.
[0025] The appearance of such stains on the walls of the bottles is
a visual defect of the product, giving the walls what is still
sometimes called an "orange peel appearance".
[0026] The present object of the present invention is therefore to
remedy these drawbacks and in particular to propose a sterilization
method and an installation that are simple and inexpensive.
[0027] For this purpose, the invention provides a sterilization
method of the type described above, characterized in that it
comprises at least the steps consisting, in succession: [0028] (a)
in checking that the preform is at a temperature below the
temperature of condensation of the sterilizing product; [0029] (b)
in spraying a flow of sterilizing agent in the form of a vapor jet
onto the preform so as to cause a substantially uniform film of a
mist of the sterilizing agent to be deposited by condensation on at
least one internal wall of the preform to be sterilized; and [0030]
(c) in radiatively heating the preform thus treated in order to
bring it to a temperature equal to or above the temperature for
activating the sterilizing agent so as to sterilize at least the
internal wall of the preform.
[0031] Advantageously, the sterilization method includes an
additional sterilization step consisting: (d) in spraying a flow of
sterilizing agent in the form of a jet of vapor onto the preform
preheated to a specified temperature.
[0032] Advantageously, the temperature to which the preform is
heated is substantially equal to the temperature at which the
preform is blow-molded, which temperature is respectively above the
activation temperature and above the evaporation temperature in
order to eliminate the sterilizing agent by evaporation.
[0033] The invention also provides an installation of the type
described above, characterized in that, at the first, spray
station, the flow of sterilizing agent is vaporized on each
preform, the temperature of which is below the condensation
temperature of the sterilizing agent so that a substantially
uniform film of a mist of the sterilizing agent is deposited by
condensing on the internal wall to be sterilized, and in that the
sterilization unit includes an activation station for activating
the sterilizing agent, comprising radiative heating means
constituting the oven for heating each preform thus treated to a
temperature equal to or above the activation temperature so as to
sterilize at least the internal wall of the preform.
[0034] According to other features of the invention: [0035] the
heating means of the activation station consist of the oven of the
thermal conditioning station so that each preform is heated to a
molding temperature which is respectively above the activation
temperature of the sterilizing agent and above the evaporation
temperature in order to eliminate the sterilizing agent by
evaporation; [0036] the molding station of the forming unit
includes at least one mold and at least one associated blowing
device which subjects each preform to an internal overpressure so
that each sterilized preform takes the form of the impression of
the mold in order to produce the sterile bottle; [0037] the mean
spray axis (A2) along which the nozzle for vaporizing the
sterilizing agent sprays the latter toward the neck is generally
parallel to the axis (A1) of the preform during treatment and
radially offset relative to the axis (A1) of the preform so as to
produce a laminar flow of sterilizing agent inside the preform;
[0038] in the sterilization unit, the preforms are generally
aligned along a longitudinal run direction (X1) and are placed in
the upright position, so as to be mutually parallel side by side,
and in that the spray axis (A2) of the nozzle is radially offset
along a direction approximately orthogonal to the run direction
(X1); [0039] the sterilizing agent consists of a compound
containing hydrogen peroxide or vaporized hydrogen peroxide, which
is activated by heating the preform above the activation
temperature; [0040] the sterilizing agent comprising hydrogen
peroxide is sprayed in the vapor state at a temperature above one
hundred and six degrees Celsius. [0041] the installation is of the
type comprising at least one transport device provided with means
for gripping the neck of each preform in order to convey the flow
of preforms through the oven, which comprises at least one means,
such as an internal core, which penetrates axially into the neck of
each preform, partly or completely obstructing the inner opening
bounded by the neck so as to increase the degree of sterilization
by increasing the time during which the internal wall of the
preform is exposed to the sterilizing agent; and [0042] the
sterilization unit includes, downstream of the oven, another spray
station, called the second station, which is intended to spray a
second flow of sterilizing agent onto each preform preheated to a
defined temperature which is at least above the activation
temperature and above the evaporation temperature of the
sterilizing agent.
[0043] Other features and advantages of the invention will become
apparent on reading the following detailed description, for the
understanding of which reference will be made to the appended
drawings in which:
[0044] FIG. 1 shows schematically a first embodiment of an
installation producing sterile bottles by blow molding and
including a sterilization unit implementing the sterilization
method according to the invention;
[0045] FIG. 2 is an axial sectional view in the plane of section
2-2, which shows schematically a preform in the sterilization unit
of the installation of FIG. 1;
[0046] FIG. 3 is a top view showing a series of preforms at the
spray station of the sterilization unit; and
[0047] FIG. 4 shows schematically a second embodiment of an
installation producing sterile bottles by blow molding and
including a sterilization unit that includes a first spray station
for implementing the sterilization method according to the
invention and a second spray station.
[0048] In the rest of the description, similar or identical
elements will be denoted by the same references.
[0049] FIG. 1 shows an installation 10 producing bottles 14, in
particular sterile or aseptic bottles, which are advantageously
obtained by blow molding plastic preforms 12.
[0050] This type of installation 10 is for example used for the
manufacture of plastic bottles 14, such as polyethylene
terephthalate (PET) bottles.
[0051] Each preform 12 is overall in the form of a tube which is
closed at one end, its other end already having the definitive form
of the neck 16 of the bottle 14.
[0052] In FIG. 2, a preform 12 is shown, by way of nonlimiting
example, with the axis Al of its cylindrical body 18 extending
vertically and coincident with the axis of the neck 16.
[0053] The lower end 20 of the preform 12 is closed, while its
upper end forms the neck 16, which defines an inner opening 22 and
is provided here with an external radial collar 24.
[0054] The preforms 12 are generally produced by an injection
molding process and are for example molded on a side other than
that where the installation 10 is located.
[0055] For some applications, the bottles 14 obtained from the
preforms 12 must have a certain degree of sterility, and this is
why it is general practice to carry out an operation to sterilize
the preforms 12 in the installation 10 for producing the bottles
14.
[0056] More precisely, the sterilization operation generally
relates to the neck 16 and the internal wall 15 of the preform 12
corresponding to the internal wall defining the internal volume of
the bottle 14 intended to be filled.
[0057] FIG. 1 shows a first embodiment of an installation 10
employing the method of sterilizing preforms 12 according to the
invention.
[0058] Conventionally, the preforms 12 are conveyed into such an
installation 10 as a continuous flow running from the upstream
toward the downstream end, that is to say from the left to the
right when considering FIG. 1.
[0059] The installation 10 comprises, from the upstream end to the
downstream end, a sterilization unit 26 for sterilizing the
preforms 12, which includes at least one spray station 28, and a
forming unit 30, for forming the sterilized preforms 12, which
includes a thermal conditioning station 32 and a molding station
34.
[0060] Advantageously, the installation 10 also includes, after the
molding station 34 of the forming unit 30, a filling unit 36 and a
stoppering unit 38.
[0061] Preferably, the sterilization unit 26 includes means (not
shown) for preparing the vaporized sterilizing agent with which the
spray station 28 is supplied.
[0062] The spray station 28 of the sterilization unit 26 is
provided with at least one nozzle 40 which, during the treatment,
sprays a flow F of sterilizing agent, in the form of a vapor jet,
here toward the neck 16 of each preform 12 to be sterilized.
[0063] Thus, the means for preparing the sterilizing agent
comprise, for example, heating means (not shown) for heating the
sterilizing agent and a supply of air (not shown), advantageously
air compressed and/or sterilized by any appropriate means, which
supply is designed to expel the vaporized sterilizing agent through
the nozzle 40.
[0064] Advantageously, the compressed air is dehydrated and flows
at low speed as a directional flow so as to constitute a carrier
for the vapor of the sterilizing agent.
[0065] Preferably, the sterilizing agent consists of a compound
containing hydrogen peroxide or vaporized hydrogen peroxide
(H.sub.2O.sub.2) which, at the spray station 28, is sprayed toward
the preforms 12 in the form of a jet of gas containing the
sterilizing agent in the vapor state, advantageously a jet of dry
vapor.
[0066] In accordance with the sterilization method according to the
invention, in particular to sterilize the internal wall 15 of the
preform 12, at least the following steps are carried out in
succession: [0067] (a) in checking that the preform 12 is at a
temperature T1 below the temperature Tc of condensation of the
sterilizing agent; [0068] (b) in spraying a flow F of sterilizing
agent in the form of a vapor jet toward the neck 16 of the preform
12 so as to cause a substantially uniform film of a mist of the
sterilizing agent to be deposited by condensing on at least the
internal wall 15 of the preform 12 to be sterilized; and [0069] (c)
in radiatively heating the preform 12 thus treated in order to
bring the preform 12 to a temperature T2 equal to or above the
temperature Ta for activating the sterilizing agent so as to
sterilize at least the internal wall 15 of the perform 12.
[0070] Advantageously, the temperature T2 is also above the
evaporation temperature Te of the sterilizing agent so as to
eliminate it by evaporation simultaneously with its thermal
activation by radiation.
[0071] Advantageously, the condensation temperature Tc of the
hydrogen peroxide is such that, when the preform 12 is at a
temperature substantially equal to the ambient temperature of the
installation 10, for example between 7.degree. C. and 35.degree.
C., which means that the vaporized sterilizing agent can easily
condense properly.
[0072] In addition, it is then simpler to check the temperature in
step (a) since it is unnecessary to modify the temperature of the
preform 12, by heating or cooling, in order for the sterilizing
agent to condense on the internal wall 15 of the preform.
[0073] The sterilization unit 26 will be described in more detail
below in relation to the features of the method according to the
invention.
[0074] The thermal conditioning station 32 of the forming unit 30
comprises at least one oven 42 which is conventionally designed to
heat the preforms 12 so as to bring them to an appropriate
temperature for molding.
[0075] The molding station 34 comprises at least one mold 44 and
here at least one blowing device 46 which subjects each preform 12
to an internal overpressure so that it adopts the shape of the
impression of the mold 44, thereby producing a sterile bottle
14.
[0076] The molding station 34 may also include elongating means
(not shown), which stretch the preform 12 toward the bottom of the
mold 44 during the molding operation.
[0077] The filling unit 36 injects the product 48 to be packaged in
the bottles 14 coming from the molding station 34 and then the
stoppering unit 38 hermetically seals the filled sterile bottles 14
with an appropriate cap 49 or, as a variant, with a membrane and/or
a stopper.
[0078] The sterilization unit 26 of the installation 10 will now be
described in greater detail according to the teachings of the
invention.
[0079] According to the invention, the sterilization unit 26 of the
installation 10 comprises, on one side, the spray station 28 for
spraying the sterilizing agent in order to carry out step (b) and,
on the other side, an activation station 50 for activating the
sterilizing agent in order to carry out step (c).
[0080] Thus, at the spray station 28, the flow (F) of the
sterilizing agent is sprayed onto each preform 12, the temperature
T1 of which is below the condensation temperature Tc of the
sterilizing agent so that a film of a mist 52 of the sterilizing
agent is uniformly deposited by condensing on at least the internal
wall 15 and the neck 16 of the preform 12 to be sterilized.
[0081] The concentration of the vapor of sterilizing agent is for
example substantially equal to twenty-five percent.
[0082] The activation station 50 for activating the sterilizing
agent comprises heating means that heat by radiation, such as
infrared radiation, in order to heat each preform 12 pretreated at
step (a) up to a temperature T2 equal to or above the activation
temperature Ta so as in particular to sterilize the internal wall
15 of the preform 12.
[0083] On leaving the nozzle 40, the vapor containing the
sterilizing agent reaches a given temperature T substantially above
the evaporation temperature Te of the sterilizing agent so that the
vapor of sterilizing agent instantly condenses on the preform
12.
[0084] In the case when hydrogen peroxide (H.sub.2O.sub.2) is used,
the temperature T at the nozzle exit is advantageously above one
hundred and six degrees Celsius (106.degree. C.), preferably
between one hundred and ten degrees Celsius (110.degree. C.) and
one hundred and twenty degrees Celsius (120.degree. C.).
[0085] When this vapor comes into contact with each preform 12,
which is colder, the vaporized sterilizing agent condenses so that
the entire preform 12, in particular the internal wall 15, is then
imbued with a film of sterilizing agent mist 52.
[0086] The nozzle 40 here is made so that the substantially uniform
film of mist 52 is deposited mainly on the neck 16 and on the
entire surface of the internal wall 15 of the preform 12.
[0087] Advantageously, the condensation deposition as a uniform
film of a mist 52 of the sterile product makes it possible,
compared with the prior art, to eliminate any risk of stains or
"orange peel" effects appearing.
[0088] The heating means of the sterilizing agent activation
station consists for example of a radiation heating oven having
heating elements.
[0089] Advantageously, the heating means of the activation station
50 consist here of the oven 42 of the thermal conditioning station
32.
[0090] Thus, the preform 12 is heated so as to reach a molding
temperature Tm which, depending on the type of preform, may vary
between 95.degree. C. and 135.degree. C., which here is above the
activation temperature Ta of the sterilizing agent and above the
evaporation temperature Te, respectively, making it possible at the
same time to eliminate the sterilizing agent by evaporation.
[0091] This is because the activation temperature Ta of hydrogen
peroxide (H.sub.2O.sub.2) is about seventy degrees Celsius
(70.degree. C.), i.e. here a temperature below the molding
temperature Tm since the molding temperature Tm is for example
between ninety-five degrees Celsius (95.degree. C.) and one hundred
and five degrees Celsius (135.degree. C.).
[0092] Of course, the molding temperature Tm depends on the type of
preform 12, this type being determined according to the
applications and the containers or bottles 14.
[0093] As is known, the oven 42 has the function in the thermal
conditioning unit 32 of reheating the preforms 12 to a temperature
above the molding temperature (95.degree. C. to 135.degree. C.) so
as thereafter to be able to carry out the molding operation in the
molding station 34, especially by blow molding the sterilized
preform 12.
[0094] However, since the radiation heating oven 42 here is common
to the activation station 50 and the thermal conditioning station
32, it therefore has two functions in the installation 10.
[0095] Specifically, the oven 42 by heating, causes, on the one
hand, the condensed sterilizing agent to be activated, which has an
immediate bactericidal effect on the internal wall 15 of the
preforms 12, and, on the other hand, the heating of the preform 12
so that it can be molded by blow molding so as to obtain the
desired sterile bottle 14.
[0096] Furthermore, since the molding temperature Tm is above the
evaporation temperature Te, the sterilizing agent is automatically
eliminated by evaporation, without requiring additional means.
[0097] In a known manner (not shown), such a heating oven 42
generally comprises a longitudinal heating tunnel, along which the
preforms 12 are transported by a transport device 54, also called a
"spinner", between a first end of the tunnel where the preforms 12
enter cold, before emerging via the second end of the tunnel heated
or reheated, ready for the blowing/molding operation.
[0098] Moreover, one wall of the tunnel is equipped with radiative
heating means, such as infrared lamps, while the other wall is
provided with aeration orifices to allow the blown air to pass so
as to favor uniform heating throughout the thickness of the preform
12 without overheating the layer of surface material.
[0099] This is because the blown air makes it possible for the
convective heat caused by the heating means to be removed in order
to favor penetration of the radiation that they produce in the
thickness of the material constituting the preform 12.
[0100] For details about such ovens 42 for heating the preforms,
the reader may for example refer to the following documents: EP-A-0
620 099 or EP-A-0 564 354.
[0101] Preferably, the oven 42 includes protection means,
especially for limiting the corrosion of the parts or components
exposed to the sterile product which, by evaporating from the
preforms 12, is thus blown into the tunnel.
[0102] Advantageously, the transport device 54 is provided with
means 56 for gripping the neck 16 of each preform 12 in order to
convey the flow of preforms 12 into the oven 42.
[0103] Document WO-A-00/48819, to which the reader may refer for
further details, describes an example of a transport device 54 of
this type, which advantageously includes means for making the
preforms 12 rotate about themselves during their passage through
the oven 42 so as to ensure depthwise heating of the preform 12,
that is to say both at the lower end 20 forming the bottom and the
cylindrical body 18.
[0104] The transport device 54 includes at least one means, such as
an internal core 58, also called a "spinner nose", which penetrates
axially into the neck 16 of each preform 12, completely or partly
obstructing the inner opening 22 bounded the neck 16, so as to
increase the degree of sterilization by increasing the time over
which the internal wall 15 of the preform 12 is exposed to the
sterilizing agent.
[0105] However, in the case of an installation 10 as shown in FIG.
1, the air blown over each preform 12 in the oven 42 removes all or
some of the film of mist 52 that can also be deposited by
condensing on the external wall of the preform 12 in the spray
station 28 of the sterilization unit 26.
[0106] This is one of the reasons, together with the fact that
sterility of the external wall is not in general desired, why the
aim of the sterilization unit 26 is essentially to sterilize the
neck 16 and the internal wall 15.
[0107] Thus, as will have been understood, what are therefore
obtained on leaving the oven 42 are preforms 12 that are mainly
sterile on the inside and that have advantageously to remain
sterile right to the final stoppering operation.
[0108] In one embodiment (not shown) of the installation 10, a
sterile confinement chamber may be provided for controlling and
maintaining the sterility of the sterilized preforms 12 and of the
bottles 14 between the various units or stations of the
installation.
[0109] Thanks to an installation 10 according to FIG. 1, a
logarithmic reduction in the number of germs of the order of 3
decimal or 3 log equivalent to 1000 units (10.sup.3).
[0110] The number of germs is for example counted in a known
manner, by counting them after washing, filtering and culturing
operations.
[0111] According to the embodiment shown here, in particular in
FIG. 3, the preforms 12 run through the spray station 28 of the
sterilization unit 26 in that they are aligned, in a vertical
position, along a longitudinal horizontal direction, called the run
direction X1, the neck 16 being uppermost.
[0112] The run direction X1 passes through the axes A1 of the
preforms 12 undergoing treatment.
[0113] Advantageously, the mean spray axis A2 of the nozzle 40 is
generally parallel to the axis A1 of each preform 12 undergoing
treatment, and this axis A2 is radially offset relative to the axis
A1 of the preform 12 by a defined offset E.
[0114] Preferably, the mean spray axis A2, which here is vertical,
is off-center along an internal radius R1 of the neck 16, which is
orthogonal to the run direction X1.
[0115] Thus, the shape of the nozzle 40 makes it possible to spray
a flow F of sterilizing agent downward generally in the form of a
laminar flow, that is to say in the form of a longitudinal vertical
curtain. For this purpose, the nozzle 40 has for example a
longitudinal slot or a generally circular hole for spraying the
flow F.
[0116] The laminar flow F here lies generally in a longitudinal
vertical plane, called the spray plane X2, which is radially offset
relative to the run direction X1 by a distance equal to the offset
E.
[0117] The flow F of sterilizing agent admits here an infinity of
mean spray axes A2, which lie vertically in the spray plane X2.
[0118] Preferably, the offset E is between a minimum E.sub.min
approximately equal to nineteen percent of the inside diameter D1
of the neck 16 of each preform 12 and a maximum E.sub.max
approximately equal to thirty-two percent of the inside diameter D1
of the neck 16.
[0119] According to one advantageous embodiment, the offset E is
chosen to be fixed and approximately equal to eight millimeters, so
that it is convenient for models of preforms 12 having inside
diameters D1 ranging between about twenty-five and forty-two
millimeters.
[0120] Thanks to such an arrangement of the nozzle 40, the flow F
of sterilizing agent is substantially flush with a first sector 60
of the internal wall 15 of each preform 12 so that the flow F of
sterilizing agent licks said sector 60 of the internal wall 15.
[0121] On arriving at the lower end 20 of the preform 12, the flow
F of sterilizing agent slides over the bottom of the preform 12 and
rises up along a second sector 62 of the internal wall 15,
diametrically opposite the first sector 60.
[0122] Thus, the flow F of sterilizing agent generally sweeps over
the entire internal wall 15 of each preform 12 by a laminar-type
flow.
[0123] Such an arrangement makes it possible in particular to
prevent the formation of an overpressure plug in the bottom of the
preforms 12, which would prevent the sterilizing agent from
reaching the bottom.
[0124] In particular, the spray rate of the sterilizing agent on
leaving the nozzle 40 is low enough to allow laminar flow.
[0125] It should be noted that the flow F of sterilizing agent
creates a mist of vaporized sterilizing agent which diffuses all
around the flow F, allowing the sterilizing agent to be deposited
over the entire area of each preform 12 and thus simultaneously
sterilizing or aseptizing the neck 16, the internal wall 15 and the
external wall of each preform 12.
[0126] A second embodiment of an installation 10' employing the
preform sterilization method according to the invention will be
described below in comparison with the installation 10 of FIG.
1.
[0127] FIG. 4 shows an installation 10' capable of producing
sterile bottles by blow molding preforms sterilized in accordance
with the invention.
[0128] The preforms 12 are conveyed through the installation 10' as
a continuous flow that runs from the upstream end toward the
downstream end, that is to say from the left to the right when
considering FIG. 4.
[0129] The installation 10' according to FIG. 4 differs mainly from
the installation 10 according to FIG. 1 in that the sterilization
unit 26 includes an additional spray station 29, called the second
spray station.
[0130] The second spray station 29 is placed downstream of the
thermal conditioning station 32 of the forming unit 30 formed by
the oven 42, which combines the function of the activation station
50 of the sterilization unit 26.
[0131] The installation 10' comprises, from the upstream end toward
the downstream end: a first sterilization unit 26 for sterilizing
the preforms 12, comprising what is called the first spray station
28; an activation station 50 formed by the oven 42; a second spray
station 29; then a forming unit 30 for forming the preforms 12,
comprising a thermal conditioning station 32 and a molding station
34.
[0132] Advantageously, the installation 10' includes, downstream of
the molding station 34 of the forming unit 30, a filling unit 36
and a stoppering unit 38.
[0133] The stations 28, 32, 50 and 34 and the units 36, 38 are
analogous to those of FIG. 1 described above.
[0134] Preferably, the sterilization unit 26 includes means (not
shown) for preparing the vaporized sterilizing agent in order for
the first spray station 28 and/or the second spray station 29 to be
supplied.
[0135] The second spray station 29 of the sterilization unit 26 is,
like the first station 28, provided with at least one nozzle 40
which sprays, during the treatment, a flow F of sterilizing agent
in the form of a jet of vapor, here toward the neck 16 of each
preform 12 to be sterilized.
[0136] Thus, the means for preparing the sterilizing agent comprise
for example means (not shown) for heating the sterilizing agent and
a source (not shown) of air, advantageously air that is compressed
and/or sterilized by any appropriate means, which is designed to
expel the vaporized sterilizing agent through the nozzle 40.
[0137] Advantageously, the compressed air is dehydrated and flows
at low speed as a directional flow so as to form a carrier for the
sterilizing agent vapor.
[0138] Preferably, the sterilizing agent consists of a compound
containing hydrogen peroxide or vaporized hydrogen peroxide
(H.sub.2O.sub.2) which, in the second spray station 29, is sprayed
onto the preforms 12 in the form of a jet of gas containing
sterilizing agent in the vapor state, advantageously a jet of dry
vapor.
[0139] In accordance with the sterilization method according to the
invention, steps (a), (b) and (c) are carried out in succession so
as to sterilize at least the internal wall 15 and the neck 16 of
the preform 12 with a logarithmic reduction in the number of germs
of the order of 3 decimal or 3 log.
[0140] Thus, as previously, deposition step (b) is carried out, by
making a uniform film of sterilizing agent mist condense in the
first spray station 26, and then step (c) of heating the preform 12
in the activation station 50 for activating the sterilizing agent
is carried out.
[0141] In the first spray station 28, the flow F of sterilizing
agent is therefore vaporized on each preform 12 which is, in
accordance with step (a), at a temperature T1 below the
condensation temperature Tc of the sterilizing agent.
[0142] In the station 50 for activating the sterilizing agent, the
preforms 12 are therefore at least heated to a temperature T2,
preferably equal to or above the molding temperature Tm and at the
very least equal to or above the activation temperature Ta.
[0143] Advantageously, the oven 42 of the thermal conditioning
station 32 constituting the radiative heating means of the
activation station 50 raises each preform 12 directly to the
molding temperature Tm, which is above the activation temperature
Ta of the sterilizing agent and here above the evaporation
temperature Te, so as to eliminate it by evaporation.
[0144] Advantageously, the heating oven 42 simultaneously exerts in
the installation 10' the function of the thermal conditioning
station 32 and the function of the activation station 50, both for
the first spray station 28 and for the second spray station 29.
[0145] The second spray station 29 of the sterilization unit 26,
which is intended to treat the preforms 12 in an additional
sterilization step so as to achieve, both on the internal wall 15
and on the neck 16, a logarithmic reduction in the number of germs,
which is either greater than 3 decimal or 3 log, will be described
below in greater detail.
[0146] After the preforms 12 have been heated by the oven 42 of the
stations 32, 50 to the defined temperature T2, they then pass
directly into the second spray station 29 located downstream in
order to undergo therein the additional sterilization step (d).
[0147] Advantageously, the heating temperature T2 is equal to or
above the molding temperature Tm, for example between ninety-five
degrees Celsius (95.degree. C.) and one hundred and thirty-five
degrees Celsius (135.degree. C.).
[0148] Now, since the preforms 12 are at a temperature above the
activation temperature Ta, for example of the order of about
seventy degrees Celsius (70.degree. C.) in the case of hydrogen
peroxide (H.sub.2O.sub.2), within the second spray station 29 there
is no deposition by the condensing of a uniform film of a mist of
the sterilizing agent as previously in the first spray station
28.
[0149] This is because the sterilizing agent is instantly activated
and evaporates on contact with the heated preform 12, consequently
producing a similar bactericidal effect on the entire area of the
preform 12, that is to say both on the internal wall 15 and the
neck 16 and on the external parts of the preform 12.
[0150] Thanks to the additional sterilization step carried out in
the second spray station 29, a logarithmic reduction in the number
of germs of at least the order of 5D or 5 log is advantageously
achieved.
[0151] The preforms 12 traveling through the installation 10, 10',
especially the sterilization unit 26, are here oriented vertically
with the neck 16 uppermost, that is to say in the "neck up"
position.
[0152] As a variant, the preforms 12 are oriented vertically with
the neck 16 downmost, i.e. "neck down", it being possible for the
preforms 12 to change vertical orientation within the installation
10, 10', in particular from one unit or station to another.
[0153] The installation 10, 10' therefore includes here transfer
means (not shown) that can invert the preforms 12 treated in the
spray station 28 of the sterilization unit 26 in the "neck up"
position to a "neck down" position in order to be taken up by the
transport device 54 associated with the oven 42.
[0154] It should be noted that the installation 10, 10' has been
shown with treatment units such as the sterilization unit 26, the
forming unit 30, the filling unit 36 and the stoppering unit
38.
[0155] These units are shown aligned, by way of illustration, but
these units may be arranged in a different configuration,
especially with rotating devices such as carousels (not shown).
* * * * *